It has previously been proposed to provide a digital computer system to determine the ignition angle, that is, the angle of crankshaft position with respect to a reference, typically the top dead center (TDC) position of the piston, see, for example, German published patent application DT AS No. 23 23 661. This system is suitable only to determine the firing angle, that is, spark advance, and requires a relatively complicated computer system in order to compute the firing angle.
Many measuring and test apparatus have been proposed to determine typical operating data in internal combustion engines; these other test apparatus and systems operate on analog bases. To obtain a digital output, analog-digital (A/D) converters are used. The output values, if indicated as analog values, frequently result in reading errors. The provision of additional A/D converters introduces quantitizing and truncating errors and additionally increases the costs of the overall system since the A/D converters are an additional cost factor for the overall system which operates on an analog basis.